package com.myTest.sqlSession;

import com.myTest.pojo.Configuration;
import com.myTest.pojo.MappedStatement;
import com.myTest.pojo.SqlType;

import java.beans.IntrospectionException;
import java.lang.reflect.*;
import java.sql.SQLException;
import java.util.List;

public class DefaultSqlSession implements SqlSession{
    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementId, Object... param) throws Exception {
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        List<Object> query = simpleExecutor.query(configuration, mappedStatement, param);
        return (List<E>) query;
    }

    @Override
    public <T> T selectOne(String statementId, Object... param) throws Exception {
        List<Object> objects = selectList(statementId, param);
        if(objects.size()==1){
            return (T) objects.get(0);
        }else {
            throw new RuntimeException("查询结果为空或者返回结果过多");
        }
    }

    @Override
    public int insert(String statementId, Object... param) throws Exception {
        return update(statementId,param);
    }

    @Override
    public int update(String statementId, Object... param) throws Exception {
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        return simpleExecutor.update(configuration, mappedStatement, param);

    }

    @Override
    public int delete(String statementId, Object... param) throws Exception {
        return update(statementId,param);
    }

    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        //调用JDK动态代理来为Dao实现，并返回
        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                // 底层都还是去执行JDBC代码 //根据不同情况，来调用selctList或者selectOne
                // 准备参数 1：statmentid :sql语句的唯一标识：namespace.id= 接口全限定名.方法名
                // 方法名：findAll
                String methodName = method.getName();
                String className = method.getDeclaringClass().getName();

                String statementId = className+"."+methodName;

                MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
                // 获取被调用方法的返回值类型
                Type genericReturnType = method.getGenericReturnType();
                //判断sql类型
                SqlType sqlType = mappedStatement.getSqlType();
                switch (sqlType){
                    case SELECT:
                        // 判断是否进行了 泛型类型参数化
                        if (genericReturnType instanceof ParameterizedType) {
                            List<Object> objects = selectList(statementId, args);
                            return objects;
                        }
                        return selectOne(statementId, args);
                    case INSERT:
                        return insert(statementId, args);
                    case UPDATE:
                        return update(statementId, args);
                    case DELETE:
                        return delete(statementId,args);
                    default:
                        throw new RuntimeException("sqlType类型无法识别!sqlType:" + sqlType);
                }
            }
        });
        return (T) proxyInstance;
    }
}
